1. Field of the Invention
The present invention relates to an image processing device that processes an inputted image, and an image shooting device having this image processing device. The present invention also relates to an image processing method for processing an inputted image.
2. Description of Related Art
Recent years have seen widespread use of image shooting devices that, in generating an image, reduce blur of the entire image (camera shake blur) attributable to motion of the image shooting device or the like and local blur (subject motion blur) attributable to motion of a subject (i.e., a shooting target such as a person) or the like. Examples of such image shooting devices include one having an image processing device that generates an image containing less blur from an inputted image and outputs the generated image. Use of such an image processing device so as to reduce blur eliminates the need of components such as a sensor for detecting and a device for reducing the motion of the image shooting device, and thus helps realize a compact and lightweight image shooting device.
For example, there have been proposed image shooting devices that generate a high-resolution high-noise image (a high-noise image) and a low-resolution low-noise image (a low-noise image) and generate one image (a merged image) by merging the two images together. Such image shooting devices calculate differential values between the two to-be merged images, and merge them together using merging ratios based on these differential values.
In particular, a region where differential values are large is recognized as a boundary between different images in an image that show different objects (which region can also be expressed as contours of an object shot in the image; hereinafter referred to as “edges”), and in this region, the proportion of the high-resolution high-noise image is increased. In contrast, a region where differential values are small is recognized as a region of one image showing one object, and in this region, the proportion of the low-resolution low-noise image is increased. Inconveniently, however, when the object is a moving object, all the region through which the object has moved is recognized as edges, and thus the merging ratios of the high-noise image become large in a wide region. As a result, an image containing much noise is outputted, and thus a disadvantageously unclear image is obtained. In addition, since the low-noise image is also a low-resolution image, contrast between edges and regions around the edges tends to be unclear. As a result, the differential values at the edges and the regions around the edges become large, and thus the merging ratios of the high-noise image become large in these parts as well. This results in an unclear merged image containing much noise.
Furthermore, it becomes difficult to accurately identify edges by distinguishing parts where the differential values are large due to noise contained in the high-noise image from parts where the differential values are large due to being edges. This difficulty may lead to erroneous recognition of the parts having large differential values due to noise as being edges, increasing merging ratios of the high-noise image to be unduly high to cause inconveniently large amount of noise to be contained all over the resulting merged image. Or, this difficulty may lead to erroneous recognition of the part having large differential values due to being edges as not being the edges, increasing merging ratios of the low-noise image at the edges to inconveniently reduce the resolution at the edges in the resulting merged image. These inconveniences cause the obtained image to be unclear.